Seal for enhancing pipes

ABSTRACT

A method is provided for replacing an existing service pipe carrying fluid to an outlet within a property with a replacement service pipe. In the method the outlet is disconnected within the property from the existing service pipe in such a way that both during and after disconnection fluid is prevented from escaping into the property. A desired length of replacement service pipe is then fed into the existing service pipe in such a way that during and after the feeding step fluid is prevented from escaping into the property. The outlet is then connected to the outlet end of the replacement pipe in such a way that during the connection fluid is prevented from escaping into the property and after the connection step fluid is allowed to pass to the outlet solely by way of the replacement pipe.

This is a Continuation of application Ser. No. 08/336,049 filed on Nov.4, 1994, now U.S. Pat. No. 5,551,704, which is a division of applicationSer. No. 07/566,411 filed on Oct. 23, 1990, now U.S. Pat. No. 5,482,076,which was filed as International PCT/GB89/01535 filed on Dec. 22, 1989.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for enhancing pipes, particularlyservice pipes for example by restoring to non-leak capability anexisting service pipe without removing same.

The invention also relates to a seal for use in replacing an existingpipe carrying fluid.

2. Discussion of the Background

Service pipes are often used to connect a main supply of say a fluidsuch as gas to a property such as for example, a domestic dwelling.Sometimes these existing service pipes begin to leak or otherwise becomein need of repair. Since these existing service pipes are oftenunderground, it can be a costly, time-consuming and environmentallyobjectionable operation to locate the pipe, excavate around it andeffect the necessary repairs. Moreover as the work is carried outexternally of the pipe, it is generally necessary to cut off supply atthe mains, which can mean that a series of dwellings can beinconvenienced as one main may supply existing service pipes leading toseveral dwellings. Moreover excavation can inconvenience the generalpublic as excavation might well have to take place outside the boundaryof the property affected by the need to repair/renovate the particularexisting service pipe. Moreover, the occupier of the affected dwellingcan be doubly inconvenienced in that apart from external disturbance, heor she has to suffer additional disturbance inside the dwelling when anyreplacement service pipe is connected to any meter in the dwelling.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to seek to mitigate thesedisadvantages.

According to one aspect of the invention there is provided a method forreplacing an existing service pipe carrying fluid to an outlet within aproperty with a replacement fluid service pipe, the method comprisingdisconnecting within the property the outlet from the existing servicepipe in such a way that both during and after disconnection fluid isprevented from escaping into the property, feeding into the existingservice pipe a desired length of a replacement pipe in such a way thatduring and after the feeding step fluid is prevented from escaping intothe property, connecting the outlet to the outlet end of the replacementpipe in such a way that, during the connection fluid is prevented fromescaping into the property and after the connection fluid is allowed topass to the outlet solely by way of the replacement pipe.

According to a second aspect of the invention there is provided anobturating device for obturating or blocking a pipe whereby to cut offfluid flow along the pipe, comprising a flexible tube having aninflatable obturating part which can be inflated to obturate theinterior of the pipe against fluid flow.

According to a third aspect of the present invention there is provided aseal for use in replacing an existing fluid-carrying pipe with areplacement pipe, the seal comprising a tubular body of a flexiblematerial, the body having a rear portion for connection to the leadingend of the replacement pipe and a front portion adapted in use toprovide a barrier to the flow of fluid along the annular gap between theinternal wall of the existing pipe and the external wall of thereplacement pipe, the seal also having a membrane serving to prevent theflow of fluid through the bore of the seal, the membrane beingpuncturable or detachable to permit the flow of fluid through the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood from the following detailed description when considered inconnection with the accompanying drawings in which like referencecharacters designate like or corresponding parts throughout the severalviews and wherein:

FIG. 1 is a schematic view of a property to be fitted with a replacementservice pipe using the method according to the invention;

FIG. 2 is a plan view of an obturating device for use in the methodaccording to the invention, one operating mode being shown in full linesand a second in dashed lines;

FIG. 3 is an enlarged side elevational view of a pipe/metering systemused in FIG. 1;

FIG. 4 is a side elevational view of a first step in the method ofreplacing an existing service pipe in the system of FIG. 3;

FIG. 5 is a schematic view, partly in section of a second step in themethod;

FIG. 6 is a schematic view, partly in section of a third step in themethod,

FIG. 7 is an enlarged section view of a fourth step applicable to oneparticular version of the method;

FIG. 8 is a partially sectional view of a fifth step according to thisversion of the method;

FIG. 9 is a partially sectional view of a sixth step according to thisversion of the method;

FIGS. 10 to 18 show sequentially yet further steps in this version ofthe method, some Figures being partly in cross-section, of theinstallation of the replacement service pipe by this version of themethod;

FIG. 19 is a side view of one form of a seal to be used with areplacement service pipe in another particular version of the method;

FIG. 20 is a front view of the seal shown in FIG. 19;

FIG. 21 is a sectional view along lines XXI--XXI of FIG. 20 taken fromabove and to one side of the seal;

FIG. 22 shows the seal after attachment to the leading end of areplacement gas service pipe and about to be inserted into one end ofthe existing gas service pipe;

FIG. 23 shows a side view in section of a seal with the membrane at therear end of the seal;

FIG. 24 shows a side view of another form of the seal, and

FIGS. 25 to 34 show sequentially the steps in the other version of themethod, some Figures being partially in cross-section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 18, there is shown a method for replacing anexisting service pipe inlet 1 carrying fluid such as gas to an outletwithin a property such as a domestic dwelling "A", FIG. 1, with areplacement service pipe for the fluid. The existing service pipe 1 hasan inlet 2 connected with a main supply which supplies a service suchas, in the embodiment, gas, into the dwelling "A". The existing servicepipe inlet 2 is connected via an elbow 3, riser 4, meter valve 5, gasmeter 6 to an outlet pipe 7 in the dwelling, the meter 6 in theembodiment being positioned internally of the dwelling "A", usuallyadjacent a boundary wall where the riser 4 enters the dwelling.

The pipe 7 is connected with the meter outlet by a further elbow 8.

In order to replace the existing service pipe 2 carrying gas to theoutlet pipe 6 within the property with a replacement gas service pipe,the gas meter 6 is closed to the flow of gas by turning the meter valve5 from the "on or open" to the "off or closed" positions (respectivelyshown in FIGS. 3 and 4). The meter 6 is then disconnected from the metervalve 5 by unscrewing the meter inlet from the valve outlet pipe 9. Aknown type gland 10, which has one or more internal annular wall or seal11, is then connected to the valve outlet 9, the gland 10 being mountedon an internal obturating or bore blocking device 12 (FIG. 2) which isinserted into the gland 10 (FIG. 5).

One particular form of device will now be described but it will beappreciated that other conventional types of obturating devices can beused with the method.

The internal obturating device 12 comprises a flexible tube 13 made froma suitable material such as pvc lined with a resilient lining such as anelongate steel coil spring 14 whereby the device 12 may be drawn roundbends without collapsing or kinking of the tube 13. Adjacent the in useleading end of the device 12 there is an inflatable part in the form ofan inflatable rubber bag 15 which is inflated on passage of fluid suchas air passed down the tube 13 through a non-return valve from a source(not shown) of air under pressure to which the device is connected by aconnector. There is internally of the tube 13 and extending from theupstream to the downsteam side of the bag 15 an elongate flexibleelement which in use prevents the bag 15 from folding over whendeflated.

The device 12 also has a rotatable member such as a nylon ball 16mounted on a pivot and positioned adjacent, or in the embodimentillustrated, at the leading or downstream end of the device 12, asconsidered in use. The ball 16 guides the device 12 as the tube 13 ispushed into the existing service pipe inlet 2 through the valve 5 afterthe valve 5 has been opened, as shown in FIG. 5. There is a furthermember 17 in the form of a nylon ball upstream of bag 15, which ball 17serves to prevent snagging of the device 12 on internal obstructionssuch as corners in the pipe 2. In use, the device 12 is fed through thevalve 5 when the valve is open with the ball 16 leading until it reachesa desired position in the existing service pipe 2 as shown by the lengthof tube 13 fed in and the bag 15 is inflated so that it temporarily butcompletely blocks the interior cross-section of the existing servicepipe 2 by impinging for 360° on the internal surface thereof.

The annular seal of the gland 10 which may be of rubber or similarflexible material is defined by a wall 11 surrounding an aperture whichwall engages with the outer surface of the flexible tube 13 of theobturating device 12 in use so as to obstruct gas flow along the annulusformed between the inner wall of the existing service pipe 2 and theouter wall of the flexible tube 13. The gland seal 11 in use sealsagainst the outer wall of a replacement or auxiliary service pipe 18(FIG. 9) to obstruct gas flow along the annulus formed between the innerwall of the existing service pipe 2 and the outer wall of the auxiliaryservice pipe 18. The gland 10 is also of the type which prevents theescape of gas when there is nothing inserted into the gland ie. thegland seal or seals are arranged so as at rest to seal off the end ofthe existing service pipe. Reverting now to the sequence of operationsof the method, the obturating device 12 having been inserted and its bag15 inflated as shown in FIG. 6, the gland 10, gas meter valve 5, elbow 3and riser 4 are removed from the existing service pipe 2.

Thus it is not necessary to effect the removal of these items by turningoff the gas supply at the main.

In one manner of carrying out the method a half coupling 19 is thenpassed over the tube 13 and connected as by screwing to the free end ofthe existing service pipe 2 (FIG. 7). The half coupling 19 has aninternal annular seal 20 which has an aperture surrounded by a wallwhich engages with the outer wall of the replacement service pipe 18 soas to obstruct gas flow along the annulus formed between the inner wallof the existing service pipe 2 and the outer wall of the replacementservice pipe 18.

The half coupling 19 also has a through bore 21 which is stepped toprovide a seating for the annular seal 20, there being an entry in theform of an injection nozzle 22 into the bore 21. The half coupling 19has a flared or frusto-conical entry or mouth 23.

An open full bore valve 24 is then connected with the half coupling 19by passing the valve over the tube 13. A gland 25 is then connected tothe open full bore valve 24 by passing the gland over the tube 13 (FIG.8).

A removable internal seal 25 (FIG. 9) in the form of a rubber stopperdevice on the end of cable 26 is then inserted with a push into thereplacement service pipe 18, which is a polyethylene tube, trimmed tothe required length. The internal seal acts to seal off the bore of thereplacement service pipe 18.

The bag 15 of the obturating device 12 is now deflated, and the tube 13of the obturating device 12 is then pulled into the gland 25 (via thehalf coupling 19 and the full bore valve 24). The full bore valve 24 isthen closed, and the obturating device 12 is pulled out of the gland 25by its tube 13. The replacement service pipe 18 is then inserted intothe gland 25 and the full bore valve 24 is then opened, allowinginsertion of the replacement service pipe 18 into the half coupling 19and then into the interior of the existing service pipe 2 (FIG. 10). Thegland 25 is then disconnected from the full bore valve 24 and removed bydrawing it over the replacement service pipe 18.

The full bore valve 24 in turn then disconnected from the half coupling19 and removed by passing over the replacement service pipe 18 (upwardlyas viewed in FIG. 10) to provide the situation shown in FIG. 11 with theinternal annular seal 20 of the half coupling 19 bearing tightly on theexterior surface of the replacement service pipe 18 to prevent theescape of gas to the dwelling externally of the replacement service pipe18. Gas is prevented from escaping to the dwelling "A" internally of thereplacement service pipe 18 by the rubber stopper device 25.

A pipe crimping coupling 27 is then connected to the half coupling 19 bypassing it over the replacement service pipe 18 and cable 26 of theinternal seal (downwardly as viewed in FIGS. 12 and 13).

The pipe crimping coupling 27 comprises a cylindrical threaded member 28with a tapered or frusto-conical nose 29 which is threaded on anelongate externally threaded carrier 30 or draw means on which is alsomounted an expansible malleable member in the form of a copper tube 31which has an initially flared end 32 remote from an end which isadjacent the conical end 29 of the threaded member 28. The externaldiameters of the cylindrical parts of the member 28 and the copper tube31 are such that they just fit into the bore of the replacement servicepipe 18. The carrier 30 is inserted in the open end of the replacementservice pipe 18 after threading over the rod 26. The bore 12 of the pipecrimping device 27 at a position remote from a flared end has an annularflange of shoulder 33. The bore 32 also has a cylindrical portion 34between the shoulder 33 and the outwardly flared part of the bore 32.The cylindrical portion 34 of the bore 32 has pipe securing means in theform of two parallel radial grooves 35 forming a crimping surface. Thepipe crimping device 27 is moved towards the half coupling 19 until theflared end of the pipe crimping device 27 fits into the flared mouth orentry 23 of the half coupling in which position the flared end 32' ofthe copper tube 31 abuts against annular flange 33. The carrier 30 isthen rotated by a knurled integral knob 36 which bears against a washer37. As the carrier 30 is captive, such rotation draws the member 28inwardly (as viewed in FIGS. 12 and 13). The action draws the conicalnose 29 of the cylindrical threaded member 28 into the cylindrical partof the copper tube 31, which is trapped against the annular flange 33.Therefore, on continued rotation of the carrier 30 the member 28 isdrawn further into the copper tube 31 which is expanded radially, andeffectively "flattened" so that it becomes wholly cylindrical. Thisaction can only be accommodated by the radially adjacent part of thereplacement service pipe 18 being forced onto the crimping surface 35with the copper tube 31 becoming embedded in the polyethylene to anextent such that copper tube 31 digs into the polyethylene so that theservice pipe 18 and copper tube 31 have substantially the same internaldiameter. The carrier 30 is then rotated further to draw the member 28right through the copper tube 31, when the carrier 30 is simply removedwith the member 28 by withdrawing over the rod 26. The copper tube 31remains firmly in place wedged in the replacement service pipe 18, whichis itself firmly crimped to the crimping-surface 35. The half coupling19 and pipe crimping coupling 27 are then firmly made up into a completecoupling 38 by screwing a knurled nut 30 down (as viewed in FIG. 14)over external threads of a complementary part 40 of the half coupling19, so securing the complete coupling with the replacement service pipe18 in place (FIG. 14). The half coupling 19 and pipe crimper 27 thuscomprise respective first and further coupling elements or parts of thecomplete coupling 38.

The elbow 3 is then connected to the completed pipe coupling 38 and theriser 4 is connected to the elbow 3. The valve 5, which is open, is thenconnected to the riser 4, and a gland 41 is connected to the valveoutlet 9 as by screwing. The further gland 41 forms a seal with thecable 26 of the internal seal 25 so preventing passage of gas into thedwelling "A". The internal seal 25 is then withdrawn through thereplacement service pipe 18 and valve 5 into the further gland 41, andthe valve 5 is closed (FIG. 16). The further gland 41 is then removedfrom the valve outlet 9 with the internal seal, by unscrewing thefurther gland 41 from the outlet 9 of the valve 5 (FIG. 17). The valveoutlet 9 is reconnected to the inlet of the gas meter 6 and the gasmeter valve 5 is then returned to the open position (FIG. 18).

A flowable settable sealant such as a mastic may be injected through thenozzle 22 entry of the half coupling 19 to fill an annular space roundthe replacement service pipe 18.

Referring to FIGS. 19 to 21 the seal 50 for use in another version ofthe method, may be a molding of a synthetic resin material such aspolyethylene, and comprises a tubular body 51 having a rear portion 52for insertion into the leading end of the replacement gas service pipe18 and a front portion 54.

The rear portion 52 is provided with several circumferentially arrangedtooth-like elements 55 serving to engage and grip the internal wall ofthe replacement pipe 18 when the portion 52 is push-fitted into theleading end of that pipe. The external diameter of the portion 52 is soselected that, in use, the portion 52 forms a gas-tight fit with theinternal wall of the replacement pipe 22 as shown in FIG. 22. In use,however the outer surface of the rear portion 52 may be coated with asuitable settable adhesive so that the portion 52 adheres firmly to theinternal wall of the replacement pipe 18 upon insertion thereinto. Thereplacement pipe 18 itself is also made of a synthetic resin materialpreferably polyethylene, so allowing the seal to be heat fused onto thereplacement pipe 18 as an alternative to adhesive.

The front portion 54 comprises several spaced continuous circumferentialannular vanes 56 to 60 which are generally radially directed anddisposed at a spacing from each other along the outer wall of the seal.As shown the diameter of the vanes increases in the direction from thefront end of the seal to the point at which the rear portion 52 of theseal begins. The rearmost vane 60 forms an abuttment for thecircumferential front edge of the replacement pipe 18 as shown in FIG.22. In use, one or more and preferably all the vanes are so dimensionedas to provide a barrier to the flow of gas along any annular gap whichwould, in use, upon insertion of the seal be formed between the body 52of the seal and the internal wall of the existing gas service pipe.

The seal is also provided at its front end with a membrane 62 closingoff the bore of the seal body 52, wherein in use to prevent the flow ofgas into and through the body 52 of the seal until the membrane 62 ispunctured, or broken in some way.

In the embodiment shown in FIG. 23 the membrane 62 is located at therear end of the seal. Otherwise the seal is similar in form to thatpreviously described.

In the embodiment shown in FIG. 24, the front portion 54 of the seal hasa thicker wall 63 than that shown in FIGS. 19 to 23 so that there isformed betwen the front and rear portions an annular shoulder 64rearwardly of the last of the vanes 60. Because of this the radialextent of the vanes 56 to 60 in the seal in FIG. 24 is foreshortened incomparison to the radial extent of the vanes in the seal in FIGS. 19 to23 so that the overall radial dimension of area bounded by each vaneremains unchanged.

In addition extending radially through the wall of the front portion 54of the seal at a point disposed between the last vane 60 and theshoulder 64 is an aperture 65 for purposes to be described subsequently.

In use, as shown the front end of the replacement service pipe 18 iscaused to abut against the shoulder 64. After the rear portion 52 of theseal has been push fitted onto the end of the service pipe 18, the sealis heat fused thereto or is affixed thereto by adhesive.

Referring now to FIGS. 25 to 34 in this version of the method the firstsix steps in the method are identical to those previously described withreference to FIGS. 1 to 6 which steps are therefore common to bothversions of the method as are the components shown in these Figures.However, in the next step in the second version of the method (FIG. 25)the gland 10 is passed back over the tube 13 of the obturating device 12and is connected to the threaded end of the existing service pipe 2 asshown in the Figure.

The bag 15 of the obturating device 12 is now deflated and the tube 13of the device 12 is pulled into and out of the gland 10 (FIG. 26). Thegland seal 11 is now closed to shut the aperture and prevent the escapeof gas from the existing service pipe 2.

In the next step in this version of the method one of the types of seal50 shown in FIGS. 19 to 24 is fitted to the leading end of thereplacement pipe 18 as shown in FIG. 27. In this Figure the seal issimilar to that shown in FIG. 19 but it is preferred to use one similarto that shown in FIG. 24. The seal 50 is preferably heat fused to theleading end of the replacement pipe 18 but it could be affixed theretoby an adhesive if preferred.

The replacement pipe 18 with the seal 50 at its leading end is theninserted into the gland 10 and is pushed through the existing servicepipe 2 as far as required (FIG. 28). One or more of the vanes of theseal 50 engage with the inner wall of the existing surface pipe 2 so asto provide a barrier to the flow of gas in the direction of the gland 10along any annular gap which is, in use, upon insertion of thereplacement pipe 18 formed between the external wall of the replacementpipe 18 and the internal wall of the existing service pipe 2. Inaddition the seal membrane prevents the flow of gas into and through thebody 52 of the seal 50 and thence into the replacement pipe 18. Thereplacement pipe can be pushed in until it contacts a service tee, elbowor bend at the main (not shown). Alternatively the replacement pipe canbe pushed until it contacts a fitting such as a polyethylene to steeltransition fitting if present in the existing service pipe.

In the next stage of the method, the gland 10 is disconnected from theend of existing service pipe 10 and the gland 10 is removed from thereplacement pipe 18 by passing the gland 10 over it so that positionshown in FIG. 29 is reached. In this position the vanes on the seal andits membrane respectively prevent gas from passing into the space 70between the existing and replacement service pipes and into and alongthe bore of the replacement service pipe 18.

The replacement service pipe 18 is then cut to length in such a way thata portion 71 of it (FIG. 29) is left protruding from the end of theexisting service pipe 2.

In the next stage, both the existing service pipe 2 and the replacementservice pipe 18 are connected to a component known as a service headadaptor, one version 72 of which is shown in half-section in FIG. 30.

The service head adaptor is a two part component having a first or, inFIG. 30, a lowermost bell shaped body 73 for connection to the threadedend of the existing service pipe 2 and a second or in FIG. 30, anuppermost cylindrical head 74 for connection at a lower end 75 to theadaptor body 73 and at an upper end 76 to the elbow 3 in a subsequentstage of the method.

The body 73 terminates in a flared lowermost end, the outer surface ofwhich has flats 77 in an hexagonal formation for engagement with aspanner to screw the body 73 on to the existing service pipe 2. As willbe seen the inner surface of the lowermost end is threaded forengagement with the threads on the outermost surface of the existingservice pipe 2.

Extending upwardly and at an angle from the wall of the adaptor body 73is an injection nipple 78 for injecting a sealant into the body 73 andthence into the annular space 70 between the replacement and existingservice pipes in the manner previously described in the description ofthe first verion of the method.

Located above the nipple 78 and extending radially outwardly from theadaptor body 73 is a pressure vent stub pipe 79 which is externallythreaded to receive a cap 80 which normally closes off the vent 79.

The body 73 terminates in an uppermost portion 81 of reduced diametercompared to the lower portion 82 of the body 73, the uppermost portion81 having an internally threaded surface for engaging with theexternally threaded surface of the lower end 75 of the adaptor head 74.As will be seen the upper end 76 of adaptor head 74 is also externallythreaded for engaging with the elbow 3, as will be describedsubsequently. In addition the ends 75, 76 of adaptor head 74 areseparated by a hexagonal shoulder 83 for engagement by a spanner toenable the head to be screwed into the body 73.

The head 74 is provided internally with a radially inwardly projectingannular rib 84 at a position opposite to the shoulder 83, which rib 84,in use, the uppermost end of the replacement pipe 18 abuts via theflanged end 85 of a tubular copper insert 86. The tubular portion 87 ofthe insert is dimensioned to be a push fit within the bore of thereplacement pipe 18 whereby the flanged end 85 of the insert is seatedover the uppermost end face of the replacement pipe 18.

When engaged with the adaptor body 73 in the manner shown in FIG. 30,the head 74 forms internally therewith an annular recess serving toreceived an annular sealing olive 88 of a suitable flexible materialsuch as rubber. With the olive 88 in place screwing the head 74 into thebody 73 causes the olive 88 to be compressed against the outer wall ofthe replacement pipe 18. This is prevented from flexing inwards by thetubular wall 87 of the insert 86. Thus there is formed between theadaptor 72 and the replacement pipe 18 a gas-tight seal.

In use of the adaptor 72, first of all the body 73 is lowered over theportion 71 of the replacement pipe 18 and is then screwed onto the endof existing service pipe 2. It will be noted from FIG. 30 that theadaptor body 73 is shaped to form with the replacement pipe 18 anannular chamber 89 acting as a reservoir to receive grout or sealingcompound injected through the nipple 78 as will be subsequentlydescribed. Next, the sealing olive 88 is positioned within the part ofthe recess formed by the adaptor body 73. Then the tubular copper insert86 is push-fitted into the end of the replacement pipe 18 until theflanged end 85 engages with the end face of the replacement pipe.Finally, the lower end 75 of the adaptor head 74 is located over theprojecting end of the replacement pipe 18, there being a close fitbetween the internal wall of the end 74 and the external wall of thereplacement pipe 18, as shown in FIG. 30, and the head 74 is screwedinto the adaptor body 73 until the rib 84 engages tightly with theflanged end 85 of the insert 86. At the same time the sealing olive 88will be compressed against the wall of the replacement pipe 18 therebyproviding a gas-tight seal between the adaptor and the replacement pipe.

A liquid and settable sealant, such as a cement grout, foam or anaerobicsealant is injected through the nipple 78 into the chamber 89 and thenceinto the annular space 70 between the replacement and existing servicepipes until the space is completely fitted. Sufficient sealant isinjected so as completely to fill the space 70 from the seal 50 at theleading end of the replacement service pipe 18 to the chamber 89. Thevanes on the seal 50 form a barrier preventing the settable sealantpassing into the main to which the existing service pipe is connected.The liquid settable sealant is now allowed to set. Preferably a seal 50similar to that shown in FIG. 24 is used so that any gas or air trappedin the space 70 is expelled by the moving front of sealant through theaperture 65 and then along and out of the free end of the replacementpipe 18.

After the sealant has been allowed to set, the nipple aperture isplugged, the elbow 3 is screw connected to the upper end 76 of theadaptor head, the riser 4 is reconnected to the elbow 3 and the gasmeter valve 5 is reconnected to the riser 4. Preferably, an unused newgland 10 is then connected to the meter valve outlet 9. Then a membranepuncturing rod or tool 90 is inserted into the gland 10. The rod 90 (seeFIG. 31) is flexible and may comprise a length of steel wire sleeved ina suitable plastic such as polyethylene or pvc. The rod 90 terminates inits leading end in a point 91 which is adapted to pierce or puncture theseal membrane to permit gas to enter the replacement service pipe 18from the existing service pipe 2. The gland 10 forms with the surface ofthe rod 90 a seal preventing escape of gas from the gland to atmospherewhen the seal membrane is punctured. The meter valve 5 is opened and therod 90 is pushed through the replacement pipe 18 as shown in FIG. 31until the point 91 encounters the seal membrane. Continued pushingcauses the point 91 to pierce or puncture the membrane and allows gas toenter the replacement pipe 18.

After the puncturing step, the rod 90 is withdrawn from the replacementpipe 18, through the elbow 3, riser 4 and meter valve 5 until its point91 is located in the meter valve outlet 9 as shown in FIG. 32.

The meter valve 5 is then closed, the rod 91 is withdrawn from the gland10 which is then disconnected from the meter valve outlet 9 so that theposition shown in FIG. 33 is reached.

Finally, the gas meter inlet is reconnected to the meter valve outlet 9and the meter control valve opened to supply gas to the premises (FIG.34).

Both versions of the methods described provide for mounting areplacement service pipe in position in an existing service pipe,installation being permitted to take place within the dwelling butwithout having to turn the gas supply off at the mains.

It will be understood that the method, obturator and seal describedherein with reference to the drawings may be used to instal areplacement service pipe in an existing service pipe carrying fluidsother than domestic gas.

We claim:
 1. A seal for use in replacing an existing fluid-carrying pipewith a replacement pipe, the seal comprising:a tubular body of aflexible material, the body having a rear portion for connection to theleading end of the replacement pipe and a front portion providing abarrier to the flow of fluid along an annular gap between the internalwall of the existing pipe and the external wall of the replacement pipe,the seal also having a seal member preventing the flow of fluid throughthe bore of the seal, wherein the seal member comprises one of apuncturable seal member and a removable seal member permitting the flowof fluid through the seal, the front portion has a plurality of vanesdisposed only around an external wall of the front portion, the vanesproviding a barrier to the flow of fluid along the annular gap, andwherein the front portion includes an abutment and said abutmentcomprises one of a rear portion of one of said plurality of vanes and arear shoulder of said front portion which is abuttable against a frontedge of the replacement pipe.
 2. A seal as claimed in claim 1, whereinthe diameter of the vanes increases in the direction from the front endof the seal to the rear end.
 3. A seal as claimed in claim 1, whereinthe seal member is located at the front end of the seal.
 4. A seal asclaimed in claimed 2, wherein the seal member is located at the frontend of the seal.
 5. A seal as claimed in claim 1, wherein the sealcomprises polyethylene.
 6. A seal as claimed in claim 2, wherein theseal comprises polyethylene.
 7. A seal as claimed in claim 1, whereinthe seal comprises a molding.
 8. A seal as claimed in claim 2, whereinthe seal comprises a molding.
 9. A seal as claimed in claim 1, whereinthe body has an aperture linking the bore of the seal to an externalsurface thereof.
 10. A seal as claimed in claim 2, wherein the body hasan aperture linking the bore of the seal to an external surface thereof.11. A seal for replacing an existing fluid-carrying pipe with areplacement pipe, which comprises:a tubular body of a flexible material,the body having a rear portion for connection to the leading end of thereplacement pipe and a front portion providing a barrier to the flow offluid along an annular gap between an internal wall of the existing pipeand an external wall of the replacement pipe, the seal also having aseal member preventing the flow of fluid through the bore of the seal,the seal member being one of a removable seal member and a puncturableseal member permitting the flow of fluid through the seal, wherein thefront portion has a plurality of vanes disposed only around an externalwall of the front portion, the vanes providing a barrier to the flow offluid along the annular gap.
 12. A seal as claimed in claim 11, whereinthe diameter of the vanes increase in a direction from a front end ofthe seal to a rear end thereof.
 13. A seal as claimed in claim 11,wherein the seal member is located at a front end of the seal.
 14. Aseal as claimed in claim 11, wherein the seal comprises polyethylene.15. A seal as claimed in claim 11, wherein the seal comprises a molding.16. A seal as claimed in claim 11, wherein the seal member comprises amembrane.
 17. A seal as claimed in claim 11, wherein the body includes awall having an aperture and wherein the wall, in use, links the bore ofthe seal to the annular gap.
 18. A seal as claimed in claim 11, whereinsaid rear portion of the body is located within the leading end of thereplacement pipe.
 19. A seal as claimed in claim 11, wherein one of arearmost vane of said plurality of vanes and a rear shoulder of saidfront portion comprises an abutment which is abuttable against a frontedge of the replacement pipe.